Drier felt for paper machines



July 25, 1939. w. A. BARRELL `DRIER FELT FOR PAPERMACHINEA Filed sept. s, 1937 Patented July 25, 1939 DRIER FELT FOR PAPER MACHINES william A. Barren, north Andover, Mass., as-

signor to Lawrence Duck Company, Lawrence, Mass., a corporation of Massachusetts Application september 3, 1937, serial No. 162,271

2 Claims.

This invention relates to woven drier felts of the general type of those heretofore used in carrying damp newly formed paper around and in contact with the heated drums of the drier,

5 which is an adjunct of the paper machine, The object of the invention is to. combine with the useful features and characteristics of the dualply drier felts heretofore in use, means and provisions whereby a more rapid and more even l evaporation of moisture from the paper and from the felt itself is secured, with consequent greater economy in the manufacture of paper.

When the newly formed web of paper reaches the drier of a paper machine, much of the origl inally contained Water has been extracted by squeezing, but it is still saturated-with the water contained in the voids between its bers, which cannot be squeezed out. This residual water is driven oil? by ,heat furnished by a succession of steam heated hollow drums or cans, arranged in two series, around which, in alternation from one series to the other, the paper is carried by the aid of two drier felts of woven construction. Except in the short stretches where th'e paper passes from the drums of either series to the respectively adjacent drums of the other series, the paper is closely embraced and fully covered by the felts, wherefore the only paths for escape of moisture from the paper are through the felts on that side.

The felts are thus thoroughly wetted, and their content of moisture retards drying of the paper until they also are equallydried. v

The wetting of the felt while subjected to high temperature, i. e., a temperature somewhat above the boiling point of water, causes rapid destruction, by scorching and rotting, of thecotton or other vegetable fibers of which such felts are wholly or mainly constructed. The destructive eect is most pronounced and rapid in the portion thereof which comes next to the paper and is most highly heated. Since the advent of the drier felt described in the patent of W. L. Barrell No. 636,482, November '7, 1899, felts woven in two distinct plies connected by binder warp strands have been generally used. In this two ply construction the face ply (the ply which comes next to the paper) insulates the back ply and to a large extent protects it from destruction by heat, whereby the felt remains serviceable after 5g', the strength and integrity of the face ply have been lost. But in all such felts, both plies have been identical in construction, and equally closely woven, whereby the back of the face ply has been covered up and evaporation of water from it has been obstructed and retarded. `The water 2,047,542 and 2,047,610, granted July 14, 1936),

construction of two ply felt in which greater absorbency than previously known was achieved, l5 but do not discharge absorbed moisture rapidly enough.

The present invention solves the problem in a new manner and affords greater absorbency in the face ply and greater porosity in the back 20 plyl than was obtainedl in the prior felts, giving better and freerer access of air to the back of the face ply continuously. According to this invention the felt is made of two plies, bound together, and the outer face of the face ply is the paper-contacting face of the felt. This ply is closely woven, having a large number of ends in its warp, while the back ply is of open construction with a number of warp strands which is only a fraction of the number of Warp strands in the 3'0 face ply. A fragment of felt illustrating the preferred construction of this invention, on an enlarged scale, is shown in the drawing furnished herewith, in which-- Fig. 1 is a plan view of the face of the fragment so illustrated;

Fig. 2 is an under plan view showing only the back ply of the felt;

Fig. 3 is a longitudinal section taken on line 3-3 of Fig. l and shown on a larger scale; and 40 Fig. 4 is across section on line d-of Fig. 3.

Like reference characters designate the same parts wherever they occur in all the figures.

The face ply is composed of interwoven warp strands a and b and a filling c in a plain weave. 45 The back'ply is likewise made as a plain weave of warp strands d and e and a filling f. The two plies are tied together by binder warp strands g which are of smaller weight and diameter. and are woven under heavier tension, than the body warps of the two plies, whereby they are drawn down against the illling strands and are overlaid more or less bythe body warp strands, particularly where the latter are spread by virtue of the tension in weaving and the resistance of the llu ing strands. The same number oi picks of nlling are placed in each ply, and the binder strands are so arranged as to pass over and under picks of the nlling in the two plies alternately. substantially as shown in Fig. 3.

The number of warp strands d, e in the baci: ply is only a fraction of the number ot strands a, b in the face ply. In the felt illustrated, the fraction is one half. These warp strands of the back ply may be equally spaced, as shown. and in that case they are preferably more or less staggered with respect to the warp strands on the back of the face play, somewhat as illustrated in Fig. 4. That is, where any warp strand in the back ply crosses a lling strand at the side next to the face ply, as shown with respect to the' strands d, din Fig. 4, it bridges across the space between two of the strands a, a in the back of the face ply, leaving these strands largely uncovered and accessible to the air. And the strands crossing outside of the filling at the rear face of the back ply are held away from the face ply.

Thus a great many points of contact are established between the face of the felt and the paper and paths are aiorded for direct evaporation and passage of vapor from the face ply di. rectly into the air, and for access of air directly to the inner face of this ply, in a manner never accomplished prior to my invention, and with greater freedom and to a larger extent than in the felts of my within named prior patents. Much of the vapor which leaves the face ply passes directly into the air without going through the strands of the back ply. Consequently less water is absorbed by the back ply than heretofore and the strands of the back ply, being in open exposure to the air, are more quickly dried. By virtue of this invention, the paper is not only more quickly and economically dried, but it is also dried more evenly.

In the form of the inventionshown in the drawing all of the strands are of cotton; there are 32 ends of warp in the face ply per `inch of width equally distributed between two harnesses; 16 ends of warp per inch of width in" the back ply, equally distributed between two harnesses; 8 ends of binder warp controlled by a singie harness; and 27 picks of filling per inch-of length in the whole felt. The body warp and lling strands of both plies are five ply, i. e., made of live single yarns of the same weight twisted together, and the binder warp strands are three.

ply and made of ner yarns. These values, however, are illustrations given for the benefit and instruction of those skilled in the art, but are not such variations, one of which, referred to illustratively, contains 40 warp strands per inch of width in the face ply; 10 warp strands in the back ply; and 10 binder strands; the warp strands in each ply being controlled by two harnesses and interwoven with the filling in a plain weave. As the construction of the alternative felt last mentioned is the same as that previously described, except for the dlierence in number of warp strands, I have deemed it unnecessary to show it in the drawing.

In any case, the face ply is closely woven, with its warp strands crowded closely together in a manner such as to resist and substantially prevent contraction in width, and elongation other than that due to the elasticity of the strands, when in use.

',While cotton is the preferred material for the feltsV of this invention, it is not the only possible material, and I may use strands of any other materials which have adequate strength, pliabi1 ity and absorbency, including not only those which have been used in drier manufacture heretofore, but others which may by test and experience be :found satisfactory hereafter. Strands or fibers of sucn other suitable materials may be combined with cotton strands or fibers or with one another, for either the body warp or the filling of either or both plies, or for the binder strands.

What I claim and desire to-secure by Letters Patent is:

"1. A drier felt of the type having a face ply and a back ply each constructed of plain-woven warp and filling strands, and the plies being connected together by interwoven binder strands; in which the warp strands of the face ply are more numerous than the warp strands of the back ply,

. in the order of from nearly twice to more than the felt.

422. A drier felt of the type having a face ply and a back ply, each constructed of plain-woven warp and nlling strands fand of which the plies are connected together by interwoven binder strands;

in which the warp strands of the face ply are at least twiceas many in number as the Warp strands of the back ply, while being of substantially equal 4diameter and Weight, and are so closely crowded together laterally as substantially to prevent contraction and elongation of the felt in use;'and the warp strands of the back ply are spaced apart from one another sufficiently to afford a substantially uniform porosity throughout the area of` said ply; the binder strands vbeing relatively small in proportion to the bodywarp strands.

- WILLIAM A. BARRELL. 

